Added Gitter badge

Author: gitter-badger

README.md

@@ -1,3 +1,5 @@
 # Android Code Reading History
 
+[![Join the chat at https://gitter.im/AndroidFrameworkCodeReading/CodeReadingHistory](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/AndroidFrameworkCodeReading/CodeReadingHistory?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+
 Android Code Reading History